RATIONALE: Bortezomib may stop the growth of cancer cells by blocking some of the enzymes needed for cell growth. Drugs used in chemotherapy, such as melphalan, work in different ways to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing. Ascorbic acid may help melphalan work better by making cancer cells more sensitive to the drug. Giving bortezomib together with ascorbic acid and melphalan may kill more cancer cells.